Summary: Noticed this in the schema. "Touches" were an idea that never really got off the ground, as we built out more/better notification channels instead. Essentially, they recorded any object you'd ever interacted with. Maybe this will be useful some day, but for now it does nothing and can't be interacted with. Nuke it.
Test Plan: `grep`, loaded Maniphest.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Differential Revision: https://secure.phabricator.com/D6953
